The context in which a stimulus appears can have a profound effect on how it is perceived and processed by the human brain. For example, the neural response to a visual stimulus is often suppressed when seen in a cluttered background. This effect is termed surround suppression, and its magnitude depends on the similarity of visual features between the center and surrounding stimuli. It is not yet clear what neural mechanism(s) underlie this effect, or how they may be divided in to separate processing stages. It is also not clear how differences in the spatial and functional properties of different suppression mechanisms might give rise to the various forms of spatial context effects observed in human vision. Using psychophysics, functional MRI, and electroencephalography, this project seeks to define three distinct mechanisms that contribute to surround suppression, each with different functional properties. A range of different stimulus and optical display configurations will be used to separately quantify the perceptual and neural response during short-range, mid- range, and long-range suppression. This will provide insight into the neural underpinnings of spatial context effects that play an important role in a number of visual processes including edge detection and figure-ground segmentation. Differentiating these mechanisms may also elucidate contextual processing strategies conserved across many brain systems, and how such processes may become disrupted in clinical conditions such as schizophrenia, autism spectrum disorder, and amblyopia.